Missouri is set to execute a convicted killer. His lawyers say new DNA evidence proves he’s innocent.

Missouri plans to put a 48-year-old man to death Tuesday, even as his lawyers say new DNA evidence proves his innocence.

The execution of Marcellus Williams is scheduled for 7 p.m. ET, but lawyers for the death row inmate have asked the US Supreme Court to stop the execution and examine the new evidence.

A brief filed Monday night with Associate Justice Neil Gorsuch said the appeal is not based on witness recantation.

“In this case, there is conclusive scientific evidence that another man committed the crime,” the brief written by defense lawyer Kent Gipson said.

But the Missouri Attorney General’s Office argues the execution should be carried out because the DNA evidence doesn’t overcome non-DNA evidence that connects Williams to the crime.

Lawyers: His DNA isn’t on murder weapon

Williams was convicted in the death of Felicia Gayle, 42, a former reporter for the St. Louis Post-Dispatch newspaper who was stabbed 43 times inside her home in August 1998.

The newly acquired evidence shows Williams’ DNA was not found on the murder weapon, Williams’ lawyers say, though DNA from another male was found.

That evidence was not available when Williams went to trial in 2001, court documents say. Williams maintains his innocence and says he was convicted on the testimony of individuals who were themselves convicted felons.

Forensic DNA expert and biologist Greg Hampikian, who was hired by defense lawyers, told CNN on Monday that “when you’re stabbing, DNA transfers because of restriction and force. If you’re stabbing anyone, you have a good chance of transferring your DNA because of that force.”

The analysis of DNA on the knife “isn’t enough to incriminate someone, but it is enough to exclude somebody,” he said. “It’s like finding a Social Security card with some blurred numbers. There’s still enough there to at least exclude someone.”

Hair samples found at the crime scene don’t match Williams’ DNA, Hampikian said. A footprint also does not match the defendant’s shoes, defense lawyer Larry Komp said.

But the Missouri Attorney General’s Office, in addressing the new DNA evidence in court documents filed in opposition to a stay of execution, offered a possible explanation of why none of Williams’ DNA was found on the knife.

State confident in his guilt

The new DNA evidence “does not come close to showing Williams is actually innocent, the documents state. It would be unsurprising if Williams, who wore a coat from the crime scene to cover his bloody shirt, wore gloves when he committed the burglary and the murder,” the documents say.

In a statement issued Monday, the state attorney general’s office said Williams’ guilt was proven without DNA evidence.

“Based on the other, non-DNA, evidence in this case, our office is confident in Marcellus Williams’ guilt and plans to move forward,” said Loree Anne Paradise, deputy chief of staff for Missouri Attorney General Josh Hawley.

The non-DNA evidence includes a laptop belonging to the victim’s husband, which Williams sold and police recovered, and some of the victim’s personal items, which police found in the trunk of the car Williams drove, according to court documents.

Williams got picked up on unrelated charges. His cell mate from that time, Henry Cole, and Laura Asaro, Williams’ girlfriend, testified for the state, saying Williams told him them separately that he committed the murder, according to the documents filed by the state attorney general.

Rejected by state Supreme Court

The US Supreme Court has not yet ruled on the motion. Normally, it waits until the day the sentence is due to be carried out to rule because death penalty lawyers often flood the court with last-minute petitions in the hours before a scheduled execution.

The Missouri Supreme Court on August 15 turned down defense lawyers’ bid to have the execution stopped and didn’t provide a reason, according to the St. Louis Post-Dispatch.

The case has drawn high-profile advocates. Sister Helen Prejean, the Roman Catholic nun who fights the death penalty and was featured in the movie “Dead Man Walking,” is involved in the case. Amnesty International is urging Gov. Eric Greitens, a Republican, to grant clemency.

“It’s gaining public attention,” Amnesty International researcher Rob Freer said of the case. “I think there is a heightened sensitivity that it is now proven that the capital justice system” has errors, he said.

The governor’s press officer, Parker Briden, declined to comment until the governor makes a final decision.

Son: ‘He’s going to be murdered’

The execution would be carried out at the prison in Bonne Terre. Defense lawyer Komp told CNN his client is taking events calmly.

“Given the tenets of his religion (Islam) that he is very devout about, he believes it will be Allah’s will and he is at peace with that,” Komp said. “Whatever will be will be. It’s astounding.”

Williams’ son, Marcellus Williams II, said his father is not one to show pain.

“He’s at peace. I think tomorrow he’s going to be murdered. He (is) an innocent man, and that’s not right,” the younger Williams told CNN Monday.

Williams II says he’s never doubted his father’s innocence and credited him with being a strong influence in his life.

“Someone murdered that woman, but it wasn’t my father,” he said. “I wish they would find the right suspect and charge them to the fullest extent of the law.”

Gayle’s widower, Dan Picus, is declining interviews, according to his wife.

In an editorial titled, “The death penalty debate hits close to home this time,” the Post-Dispatch remembered Gayle and said she would not have favored the execution.

She “was a kind and gentle woman who went out of her way to do nice things for people. She’d left the newspaper in 1992 to do full-time volunteer work.”

The editorial said the paper “opposes capital punishment under any and all circumstances, believing its administration is always arbitrary and always irrevocable. It has no deterrent value. If the state must execute, there must be no room for doubt.”